1. Field of the Invention
The present invention relates to the field of the use of refined agricultural materials, particularly cellulosic fibers and more particularly highly refined cellulosic fibers especially those fibers having relatively high concentrations (greater than 5% total weight) parenchyma cell wall source. A particularly desirable use of these highly refined cellulose fibers is in the manufacture of gels, and particularly gels that can be used as thickening agents. The present invention also relates to the field of preparing highly refined cellulose fiber products from pectin-containing plant materials, including a method for providing fiber-containing pectin products from parenchyma cell wall materials.
2. Background of the Art
In the industrial production of food and beverages, many byproducts are produced that are fibrous in nature and contain cellulose, hemicelluloses and pectin. By-products or waste products examples include: sugar beet slices from the production of sugar from sugar beets, citrus peels and citrus pulp from the manufacture of juice and ethereal oils from citrus fruits, pomace residues from cider production, and potato fibers from potato processing. These plant by-products are often considered as waste products to be disposed of in the most appropriate and most inexpensive way. However, it will be understood that there may be quite obvious advantages by further developing such plant by-products into products of more commercial value.
Parenchymal cell walls refer to the soft or succulent tissue, which is the most abundant cell wall type in edible plants. For instance, in sugar beets, the parenchyma cells are the most abundant tissue the surrounds the secondary vascular tissues (xylem and phloem). Parenchymal cell walls contain relatively thin cell walls compared to secondary cell walls are tied together by pectin (Haard and Chism, 1996, Food Chemistry, Ed. by Fennema, Marcel Dekker N.Y., N.Y.) In secondary cell walls (xylem and phloem tissues), the cell walls are much thicker than parenchymal cells and are linked together with lignin This terminology is well understood in the art.
A common feature of these by-products is that they consist essentially of soluble and insoluble plant fibers, of which about 50-90% are dietary fibers, including three biopolymers: cellulose, hemicellulose and pectin involved in the structure of all plant cell walls, which can be conceived as a cellulose-hemicellulose-pectin network in which pectin, apart from being a structural element, also constitutes the “cement” imparting rigidity to the plant cells. This complex structure in which pectin is attached to the other cell wall components by covalent bonds, hydrogen bonds, and/or ionic interaction is often termed protopectin. Purified pectin, per se, can be obtained by controlled, acidic or basic hydrolytic extraction of protopectin. Purified pectin is a linear polymer composed of units of a-D-galacturonic acid attached by a-1,4-glycoside bonds to form long chains of polygalacturonic acid. The galacturonic acid units are esterified with methanol to a varying degree. A distinction is thus made between high-ester pectin having a degree of esterification (DE) of greater than 50% and low-ester pectin having a degree of esterification of less than 50%. The degree of esterification is defined as the number of methyl-esterified galacturonic acid units expressed as a percentage of the total galacturonic acid units in the pectin molecule and may thus be a value between 0% and 100%. In pectin from some types of plant material, e.g. potatoes and sugar beets, a varying part of the galacturonic acid units may, in addition, be acetylated, expressed as the degree of acetylation (DAc), which is defined, analogous to the degree of esterification, as the number of acetylated galacturonic acid units as a percentage of all galacturonic acid units. Neutral sugars, such as galactose, glucose, rhamnose, arabinose and xylose, may also be part of the pectin polymer as side-chains to or as members in the polygalacturonic acid chain. Hemicellulose is a heterogeneous group of polysaccharides containing several kinds of hexose and pentose sugars and, in some cases, residues of uronic acid. These polymers are classified according to the type of sugar residues being dominant and are individually referred to as xylans, arabinogalactans, glucomannans and so on.
Present endeavors to find utility for these fiber residues include methods of refining the fiber mass and compositions and treatments of the refined (highly refined cellulose are described in the following U.S. Published Applications and Patents: 20120142909 (Viscosity Control in Compositions Comprising Plant Fiber Materials); 20110268860 (Novel Dairy Product Compositions Using Highly Refined Cellulosic Fiber Ingredients), now U.S. Pat. No. 8,399,040; 20090274811 (Defect Separation from Dry Pulp); 20090269376 (Stabilization Of Cosmetic Compositions); 20080193590 (Highly Refined Cellulose Neutraceutical Compositions and Methods of Use); 20080166464 (Moisturizing Composition for Protein Materials); 20060251789 (Novel Dairy Product Compositions Using Highly Refined Cellulosic Fiber Ingredients); 20060210687 (Enhanced Crackers, Chips, Wafers and Unleavened Using Highly Refined Cellulose Fiber Ingredients); 20060204631 (Cellulose Fiber-Based Compositions and Their Method of Manufacture) now U.S. Pat. No. 7,074,300; 20050274469 (Highly Refined Fiber Mass, Process of Their Manufacture and Products Containing the Fibers) now U.S. Pat. No. 7,094,317; 20050271790 (Reduced Fat Shortening, Roll-in and Spreads Using Citrus Fiber Ingredients); 20050074542 (Highly Refined Cellulosic Materials Combined with Hydrocolloids); 20040086626 (Highly Refined Fiber Mass, Process of Their Manufacture and Products Containing the Fibers); 20030116289 (Cellulose Fiber-Based Compositions and Their Method of Manufacture) now U.S. Pat. Nos. 6,506,435; and 7,582,213 (Cellulose Fiber-Based Filters). These applications and are incorporated in their entirety, especially with respect to the disclosed technology in manufacturing highly refined cellulose, and citrus pulp-based highly refined cellulose and their physical and chemical properties.
U.S. Pat. No. 5,567,462 discloses a method of preparing pecto-cellulosic compositions and pectin from pectin-containing plant raw materials, such as citrus peels, sugar beet pulp, sunflower residues, and pomace residues. The method consists of treating the comminuted plant raw materials with an acid, e.g., phosphoric or nitric acid, or with a base, e.g., sodium hydroxide or sodium carbonate, to give a mixture consisting of a solid phase containing cellulose components and a liquid phase containing dissolved pectin. The mixture is mashed, neutralized and finally dried to form pecto-cellulosic dry matter. The mashed mixture may also be separated into a solid and a liquid phase, which are neutralized individually and dried to give a pectin product and a pecto-cellulosic product.
It is also known in the prior art how to de-esterify pectin or a pectin-containing material with aqueous ammonia in an organic solvent, e.g. isopropanol, in which pectin is non-soluble. This technique is for example disclosed in U.S. Pat. No. 2,480,710.
U.S. Pat. No. 7,833,558 (Larsen et al., also referred to herein as the “KMC Patent”) asserts a method whereby, without dissolving pectin and without using organic solvents, it is possible to carry out the de-esterification of pectin in an entirely aqueous system in the treatment of a pectin-containing plant material, which has been swollen in an aqueous solution containing neutral salts prior to the de-esterification treatment. The method includes providing a pectin product, said method comprising the steps of: (i) providing an in situ reaction system by swelling the plant material in an aqueous solution, wherein said aqueous solution comprises at least one salt; (ii) subjecting pectin present in the swollen plant material from step (i) to a de-esterification treatment in the presence of an alkaline reagent; and (iii) separating the de-esterified fiber-containing pectin product, wherein the alkaline reagent provided in step (ii) results in a pH above 10. The method may include further steps of (iv) adding an extraction medium to the fiber-containing pectin product providing an extraction suspension; (v) adjusting the pH of the extraction suspension to a pH in the range of 1-12; (vi) adjusting the temperature of the extraction suspension to a temperature in the range of 0-120° C.; and (vii) isolating the pectin product from the aqueous phase of the extracting medium. This method produces significant alkaline waste and is reagent intense in the mounts of alkaline materials, in part because of the high pH levels used to de-esterify the pectin.
The present invention may provide a simple method of treating highly refined cellulose fibers, especially citrus pulp-based highly refined cellulose fibers, including highly refined pectin-containing plants under normally very weak de-esterifying conditions, thereby achieving fiber-containing pectin products as well as isolated pectin products of high commercial value and high practical use.